Shape determination for deformed electromagnetic cavities

The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to s...

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Bibliographic Details
Published in:Journal of computational physics 2008-01, Vol.227 (3), p.1722-1738
Main Authors: Akçelik, Volkan, Ko, Kwok, Lee, Lie-Quan, Li, Zenghai, Ng, Cho-Kuen, Xiao, Liling
Format: Article
Language:English
Subjects:
Accelerators, Math and Math Physics,ACCSYS, MATH
ALGORITHMS
CAVITIES
Computational techniques
DEFORMATION
Eigenvalue problems
EIGENVALUES
Exact sciences and technology
FABRICATION
Inverse problems
Linear accelerators
MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
Mathematical methods in physics
Maxwell equation
MINIMIZATION
OPTIMIZATION
Physics
SHAPE
Shape optimization
TUNING
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Summary:The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to solve for the unknown deviations from the ideal cavity using experimentally measured cavity data. The objective is to match the results of the deformed cavity model to experimental data through least-squares minimization. The inversion variables are unknown shape deformation parameters that describe perturbations of the ideal cavity. The constraint is the Maxwell eigenvalue problem. We solve the nonlinear optimization problem using a line-search based reduced space Gauss–Newton method where we compute shape sensitivities with a discrete adjoint approach. We present two shape determination examples, one from synthetic and the other from experimental data. The results demonstrate that the proposed algorithm is very effective in determining the deformed cavity shape.
ISSN:0021-9991
1090-2716
DOI:10.1016/j.jcp.2007.09.029